The number of patients suffering from allergies is steadily increasing. For example, survey results in Japan have reported that one in three people suffer from some type of allergic disease. A reduction in the number of patients suffering from an allergic disease resulting from use of a food would have a high social and economic significance due to the resulting improvement in the national quality of life and the large decrease in medical costs.
IgE is a principal factor in immediate allergy (type-I allergy) reactions such as atopic dermatitis, hay fever or the like. IgE production is induced by B cells undergoing IgE class switching in response to interleukin 4 (IL-4). The principal source of production of IL-4 is TH2 cells. Helper T cells such as TH1 cells and TH2 cells are stimulated by presentation of antigen from cells such as dendritic cells, macrophages or the like, and follow respective differentiation paths in response to the influence of cytokines such as IL-4, IL-12, or the like. The differentiation of TH1 cells is induced by IL-12 and the differentiation of TH2 cells is induced by IL-4. When TH2 cells become particularly dominant due to collapse of the balance between TH1 cells and TH2 cells due to some reason, the effect of IL-4 is increased and IgE production is enhanced. The produced IgE binds with high-affinity IgE receptors on the cell surface of mast cells or basophils. In this state, when an antigen (allergen or the like) binds with IgE, cross-linking occurs between high-affinity IgE receptors and degranulation results in release of chemical messengers such as histamine or the like. Consequently lipid mediators such as leukotoriene are produced thereby resulting in allergic symptoms typified by inflammation. Serious allergic symptoms are observed during enhanced production of IgE.
Therapeutic agents for allergic diseases are mainly steroidal agents used as anti-inflammatory agents, or antagonists of chemical messengers, typically anti-histamine agents. All these agents are used in symptomatic treatment, and have no function of directly reducing the amount of IgE which is the main factor in pathogenesis. Furthermore the former agents entail risks associated with side effects such as drowsiness or dryness of the mouth, and the latter agents have side effects such as suppression of the overall immunity system. Medicines that can mitigate a state in which TH2 cells are particularly dominant aim to enable definitive therapy for allergies, however at present such agents have not yet been developed. Hyposensitization therapy is a therapeutic method of reducing an amount of IgE. A method of hyposensitization therapy is a therapeutic method which mitigates symptoms by ingesting (or injecting) an allergen which is the causal substance of an allergic illness commencing with a small amount and gradually increasing the amount. This therapeutic method includes a risk of anaphylaxis due to administration of the allergen, and must be performed under strict medical supervision. At the present time, hyposensitization therapy cannot be said to have been completed validated, and scope for improvement in relation to reliability remains in view of the long time required for treatment and the individual differences that are observed.
Against this background, lactic acid bacteria have attracted attention due to the rich experience in their ingestion as a food and due to their function of suppressing IgE production. The anti-allergic action of lactic acid bacteria is strain-specific. Lactic acid bacteria having this type of anti-allergic action are screened and enter the market in the form of lactic acid drinks or yoghurt.
Although continuous daily ingestion of lactic acid bacteria is necessary to profit an anti-allergic action, individual tastes may preclude consumption of yoghurt or lactic acid bacteria drinks. Furthermore it is unlikely that these foods are in an optimal configuration for daily required ingestion without a Japanese person becoming satiated. In contrast, the staple of the Japanese diet is rice, and although a tendency not to eat rice has been evident in recent years, rice is a product that will always be ingested at least in one out of three meals.
A lactic acid bacterium having an anti-allergic action can be combined with rice by mixing polished white rice with a lactic acid bacterium that has been cultivated in a separate tank or the like. However since the diameter and the specific gravity of the rice particles and those of the lactic acid bacteria are different, there is a risk that these components will separate during storage, and that only the lactic acid bacteria will sink to the bottom of a storage vessel such as a rice bag or the like. Consequently, it will not always be the case that a desired amount of lactic acid bacteria will be contained in rice even when a fixed amount of rice is measured. Consequently, there are difficulties associated with ensuring ingestion of a required amount of lactic acid bacteria in order to display an anti-allergic action. Furthermore although a technique of coating lactic acid bacteria onto the surface of the polished white rice can be used, such a technique requires complicated processing and causes cost increases.